Engineering ToolBox > NEMA A, B, C and D Design
NEMA has established four different designs - A, B, C and D - for electrical induction motors
Different motors of the same nominal horsepower can have varying starting current, torque curves, speeds, and other variables. Selection of a particular motor for an intended task must take all engineering parameters into account.
The four NEMA (National Electrical Manufacturers Association) designs have unique speed-torque-slip relationships making them suitable to different type of applications:
NEMA design A
- maximum 5% slip
- high to medium starting current
- normal locked rotor torque
- normal breakdown torque
- suited for a broad variety of applications - as fans and pumps
NEMA design B
- maximum 5% slip
- low starting current
- high locked rotor torque
- normal breakdown torque
- suited for a broad variety of applications, normal starting torque - common in HVAC application with fans, blowers and pumps
NEMA design C
- maximum 5% slip
- low starting current
- high locked rotor torque
- normal breakdown torque
- suited for equipment with high inertia starts - as positive displacement pumps
NEMA design D
- maximum 5-13% slip
- low starting current
- very high locked rotor torque
- suited for equipment with very high inertia starts - as cranes, hoists etc.
